Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C263/00—Preparation of derivatives of isocyanic acid
  • C07C263/10—Preparation of derivatives of isocyanic acid by reaction of amines with carbonyl halides, e.g. with phosgene

Definitions

• organic isocyanates As is known, the predominant part of organic isocyanates is produced by phosgenation of primary amines, their hydrochlorides or their carbonamide acid salts (cf. Ullmanns Encyklopadie der Technische Chemie, 4th edition, volume 13, page 350 ff.).
• the base phosgenation In the cold, the amine, which is in an inert solvent, reacts with excess phosgene solution (cold phosgenation): In the second step, the so-called hot phosgenation, the carbamoyl chloride cleaves above 80 ° C. to form the isocyanate hydrogen chloride. The hydrochloride also reacts to the isocyanate above this temperature:
• the competition reaction for isocyanate formation is urea formation from amine and already formed carbamoyl chloride or isocyanate.
• the ureas convert into the isocyanate only with difficulty or practically not at all. This applies particularly to aliphatic amines and very particularly to polyamines. Therefore, the process must be aimed at preventing the formation of urea.
• Prephosgenation is preferably carried out with a large excess of phosgene at the lowest possible temperature. In practice, therefore, relatively concentrated phosgene solution is introduced in excess and the amine is added in an organic solvent.
• Aliphatic amines which are more basic, are even more difficult to directly phosgenate than base. It is easier to prevent urea formation if, instead of the free amine, its carbamic acid salt is used. Prephosgenation is used.
• the carbamic acid salt is first prepared by saturating an amine solution with carbon dioxide, which is sparingly soluble and is suspended in the solvent.
• the same carbamoyl chloride-hydrochloride mixture is formed with the elimination of C0 2 as in the base phosgenation, which is then also hot phosgenated:
• the carbamate process allows less effort when mixing the amine or its carbamate with phosgene; However, it is sustainable that a third reaction stage is required and additional CO 2 is required, which can only be recovered from the exhaust gas with considerable effort.
• the stable hydrochlorides do not react in the cold and their reaction speed is comparatively slow even in the heat. Long reaction times or higher temperatures used to shorten the reaction time, however, lead to side reactions such as chlorine substitution and isocyanate polymerization reaching an undesirable extent. It is therefore difficult to carry out this reaction continuously.
• the aim of the present invention starting from the hydrochloride method, was to design the hot phosgenation step continuously in such a way that the reaction time can be shortened and the process can be carried out in one step if possible. Another goal was to achieve purer products and better yields under milder reaction conditions.
• a certain solid concentration is established in the reactor, which is increased or decreased allowance of addition and dispensing changes.
• the addition consists of amine hydrochloride or its mixture with carbamoyl chloride in a suitable solvent.
• the delivery contains the isocyanate derived with the aid of the separation device mentioned, which is present dissolved in the same solvent. Since the increase in the solids concentration increases the conversion, the highest possible concentration is aimed at, but this is limited by the fact that a flowable suspension must be retained.
• the optimal solids concentration varies depending on the amine used. For example, while the optimum for 1,5-diamino-2-methylpentane is about 20%, only about 1% is possible with isophoronediamine, since otherwise the hydrochloride would clump.
• the process according to the invention is particularly favorable when using the hydrochloride method.
• the response times can be shortened considerably.
• the isocyanates can be obtained in almost quantitative yield and very high purity.
• 1, 5-diamino-2-methylpentane enables the diisocyanate to be prepared economically.
• the average residence time can be reduced by a factor of 4.
• the hydrochloride method gives conversions which can otherwise only be achieved after previous pre-phosgenation.
• Example 4 shows that the process according to the invention can also be used advantageously if pre-phosgenation has already taken place.
• the isocyanate-containing reaction solution can be separated off in different ways. For example, part of the suspension can be branched off from the reactor and the solid separated and returned to the reactor. However, the separation can also be carried out in the reactor itself or before the product exit, the solid remaining in the reactor at all times. The separation can take place, for example, by decanting, centrifuging or using a hydrocyclone.
• the reaction solution is preferably separated off with the aid of a filter.
• the process according to the invention can be used for phosgenation of primary aliphatic, cycloaliphatic, araliphatic and aromatic mono- and polyamines with 5 to 18 carbon atoms or their technical mixtures.
• Examples include 1,3-bis (aminomethyl) benzene, aniline, toluenediamine-1, and -1, 4, 4,4'-diaminodiphenylmethane, octadecylamine, 1, 5, 9-triaminoundecane, cyclopentylamine.
• Aliphatic and cycloaliphatic diamines such as 1, 6-diaminohexane, 1,5-diamino-2-methylpentane, 1, 6-diamino-2, 2, 4- or -2,4,4-trimethylhexane, 1,9, are particularly suitable -Diamino-5-methyl-nonane and 1-amino-3-aminomethyl-3, 5, 5-trimethylcyclohexane.
• Suitable solvents are aliphatic and aromatic compounds which are inert under the reaction conditions. These contain 6 to 15 carbon atoms and may carry alkyl radicals and chlorine atoms as substituents. Examples include toluene, xylene, tetralin and decalin. Chlorobenzene with a boiling point of 130 ° C. or o-dichlorobenzene with a boiling point of 170 ° C. is preferably used . if the reaction is to take place at a higher temperature.
• the suspension supplied to the hot phosgenation contains 3 to 30 liters, preferably 10 to 20 liters, of solvent per kg of amine to be reacted.
• the method according to the invention also has advantages in these cases.
• the average residence time for the hot phosgenation of toluenediamine can be reduced from more than 6 hours (example 1 of DE-OS 15 68 844) to 2.5 hours (example 6).
• reaction solution containing the isocyanate is worked up in a conventional manner, as can also be seen from the examples.
• the diisocyanates obtainable according to the invention can be used in many ways, in particular they are suitable for the production of polyurethanes, polyureas and polyamides.
• Example 1 As described in Example 1, 300 ml of chlorobenzene solution containing 22.5 g of an isomer mixture of 92% 1, 9-diamino-5-methylnonane and 8% 1, 8-diamino-2, 4-dimethyloctane are hourly in reactor I , metered in and fed 9 1 hydrogen chloride gas. The overflowing suspension is hot phosgenated in reactor II at 122 ° C. and using phosgene at 50 l / h. At the bottom of the reactor, so much clear reaction solution is drawn off per hour (approx. 300 ml) that the reactor level is retained. Working up is as described in Example 1. When distilling, 1, 1% residue remain; the analytical yield is 98.5%.
• the carbamate suspension overflows in reactor II, in which the conversion to the carbamyl chloride hydrochloride mixture takes place at 0 ° C. with excess phosgene. 200 liters of phosgene (phosgene + fresh phosgene recovered from the exhaust gas) are introduced per hour.
• Reactor III is operated at 125 ° C.
• the phosgene required for hot phosgenation is contained in the reaction suspension which overflows from reactor II. According to the feed, 3 liters of clear solution are drawn off per hour.
• the crude diisocyanate contains only 0.1% of 1 (5) -chloro-5 (1) -isocyanato-2-methylpentane as an impurity.
• the distillation residue is 0.8% and the analytical yield is 99%.
• the phosgenation apparatus consists of 2 stirred tanks I and II with 2 or 30 liters in series.
• the hydrochloride suspension flows continuously into reactor II, into which 200 liters of phosgene / h (recovered phosgene + fresh phosgene) are introduced at 140.degree. As described in Example 4, 3 liters of clear reaction solution are drawn off every hour. The solids content in the reactor is 20%. According to the gas chromatogram, the crude diisocyanate contains 0.9% monochloroisocyanates. The distillation residue is 3.7%, the analytical yield 95%.
• the clear reaction solution passes through a heated tray column with 5 trays and a "hold-up" of a total of 500 ml. At 125 ° C, 30 l of phosgene per hour are passed upwards against the liquid flow. Further workup is carried out as described in Example 1. When distilling there remains 6.6% residue; the analytical yield is 93.2%.

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• Chemical Kinetics & Catalysis (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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• 1983
  • 1983-07-02 DE DE19833323882 patent/DE3323882A1/de not_active Withdrawn
  • 1983-09-09 EP EP83108925A patent/EP0106138B1/fr not_active Expired
  • 1983-09-09 DE DE8383108925T patent/DE3360354D1/de not_active Expired
  • 1983-10-11 US US06/540,997 patent/US4549991A/en not_active Expired - Fee Related

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